Fuel cells use the chemical conversion of a fuel that comprises oxygen in order to generate electrical energy. For this purpose, fuel cells comprise as core components the so-called membrane electrode assembly or membrane electrode unit (MEA=membrane electrode assembly) that can be embodied as a combination of the membrane that conducts ions, in particular protons, and respectively an electrode (anode and cathode) that is arranged on both sides of the membrane. The active material can comprise a catalyst or can be a catalyst that promotes the chemical conversion. In addition, gas diffusion layers can be arranged on both sides of the membrane electrode assembly on the faces of the electrode that are remote from the membrane. The fuel cell comprises at least one membrane electrode assembly or a plurality of membrane electrode assemblies that can be arranged in a fuel cell stack, wherein the power outputs of multiple membrane electrode assemblies are summated. During the operation of the fuel cell, an operating medium, by way of example the fuel, in particular hydrogen (H2) or a gas mixture comprising hydrogen, is supplied to the anode where an electrochemical oxidation of H2 to H+ takes place whilst discharging electrons. The protons H+ are transported out of the anode chamber into the cathode chamber in a water-bound or water-free manner by way of the membrane that electrically insulates and separates the reaction chambers of the fuel cell one from the other in a gas-tight manner. The electrons that are provided at the anode are conducted by way of an electrical line to the cathode. A further operating medium possibly oxygen (O2) or a gas mixture comprising oxygen is supplied to the cathode so that O2 is reduced to O2− whilst absorbing the electrons. These oxygen anions react simultaneously in the cathode chamber with the protons that are being transported by way of the membrane whilst forming water. By virtue of the direct conversion of chemical energy into electrical energy, fuel cells achieve an improved level of efficiency in comparison to other electrical generators by avoiding the Carnot factor.
In order to prevent that hydrogen collects in undesired concentrations in a housing of the fuel cell, housings of known fuel cells are ventilated with the aid of a ventilator. Furthermore, if the fuel cell is not operating, hydrogen can collect between the anode side and the cathode side of the membrane electrode assembly as a result of a connection that is conducting gas. If the fuel cell is brought back into operation, said fuel cell is flushed out on the cathode side so that in turn undesired hydrogen concentrations can be contained in the cathode gas that has been flushed out. These concentrations are reduced in the case of known fuel cells by adding a diluting gas, in particular air, wherein the diluting gas is supplied by means of additional gas supply lines to the gas that is to be diluted. By way of example, a fan is also required to transport the diluting gas. The known methods for preventing undesired high hydrogen concentrations are however costly and require installation space. Furthermore, energy is required at least to operate the ventilator and this constitutes an additional electric consumption.
The object of the invention is to provide a fuel cell arrangement that can be constructed and operated as small as possible and in a simple manner as possible.